1. Field of the Invention
The invention relates to the field of telecommunications, and particularly to high-speed data transmission over fiber optic networks.
2. Description of Related Art
Synchronous Optical Network (“SONET”) rings provide infrastructures for high capacity data transmission over fiber optic cables. Defects or failures on a SONET ring can occur in several places such as defects on a fiber or in equipment, or defects in processing a received signal. Traffics transmitted over a SONET ring include standard synchronous data (e.g., DS1, DS3), Asynchronous Transfer Mode (ATM), and various types of packets such as IP and Frame Relay (FR). ATM and standard synchronous connections provide end-to-end monitoring mechanisms which allow a transmitting node and a receiving node to monitor communication links. The monitoring functions of ATM and standard synchronous connections are capable of detecting defects, whether a defect occurred at a source, destination or intermediary node. If a protection or redundant fiber path is provided, protection switching is then made from the defected working fiber path to the protection fiber path to recover traffic.
However, such end-to-end monitoring mechanism is not available in FR. FR monitors a communication link connected directly between two nodes. FR provides no mechanism for monitoring a communication link where an intermediary node is placed between two end nodes. When a failure occurs at an intermediary node, FR traffic provides no notification of the defect to other nodes on a SONET ring.
Accordingly, it is desirable to have a protection method and system for recovering FR traffic when a failure occurs in a SONET ring.